In a medium saucepan, bring Turkey Gravy Flavor packets and chicken stock to a boil. (If you have turkey drippings, add those in. To replace the flavor packs, you need 2 cups of strained drippings.)
Create a slurry in a separate bowl or mug with flour and hot water. Stir hot water and flour until there are no lumps.
Whisk slurry into the saucepan a little at a time until you get the consistency of gravy you prefer. The gravy should start to thicken within a few minutes.
Add 1 cup of milk and 1/4 cup of butter.
Taste test and adjust with salt and pepper. If the gravy is to thin, add more slurry. If the gravy is too thick, add more chicken stock.